Horseshoes which attenuate vibration energy from the horseshoes to the leg of the animal, especially of race horses.
A 1500 pound race horse running at perhaps 30 miles per hour places a heavy impact load on its feet. Especially there is a peak shock load at the moment of impact. A metal horseshoe is shaped as a U, and a blow on it will cause it to vibrate, essentially to xe2x80x9cringxe2x80x9d.
The shoe is tightly attached to the hoof by nails so the ringing vibration is readily transmitted to the animals""s leg. In addition this energy works on the nails, adding to the tendency of the nails to loosen as the result of flexure of the hoof itself.
Shoes are often thrown during vigorous exercise and racing and must be carefully watched. Expensive race horses may need to be re-shod as frequently as every four to five weeks. It is an economic advantage to lengthen this period, especially for less valuable horses whose earnings cannot support optimum care.
A well-known horseshoe which dampens and thereby reduces the vibrations, and which is intended to reduce the peaks of the impact force loads, is the No-Vibe horseshoe manufactured and sold by the inventor herein, and available from No-Vibe Co., 1620 Bluebird Road, Glendora, Calif. 91741. It constitutes a metal shoe with a layer of shock-absorbing solid organic plastic material cemented to the upper surface of the metal shoe. When the animal is shod, nails are pounded into the hoof through the shoe with the pad bearing against the hoof. The pad is disposed between the metal shoe and the hoof itself.
When the front foot of a running horse first strikes the ground, it lands with its hoof tilted up. The rear end strikes first, the rear end is the open end, with the points of the horseshoe pointing toward the rear. Then as the horse moves forwardly the bottom of the hoof tilts forwardly. The forward end (with the bight and perhaps a cleat) engages the ground and digs in, and the hoof tilts still more as it leaves the ground. This all occurs very quickly.
There is an additional component of motion of the hoof. Its movement is not a simple forward tilt as suggested above. Instead, immediately upon impact the hoof begins a twisting motion around the hoof axis. This put an additional shear force on the cement layer which holds the pad to the metal shoe. Reduction of vibration relies heavily on a tight intimate joinder of the pad and the shoe, as well as of the pad and the hoof.
Retention of the pad by the cement and the nails is quite effective over most of the area of the shoe, especially in its center bight and along most of its arms. However, the situation is more complicated near the free end of the arms. For about the last inch of each arm there is insufficient hoof material to receive a nail, so unless other retention is provided, the cement layer must take all of the shear load when the pointed ends first strike the ground. In addition, because these two ends do strike the ground first, there is a strong force tending to peel the pad from the metal shoe.
In the previously mentioned No-Vibe horseshoe, this situation was countered by riveting the pad to the metal shoe with a countersunk rivet whose head is sunk in the pad. This has been generally successful, except that if the pad wears too much, the rivet head becomes exposed and may contact the hoof. This can cause a corn on the hoof, which is intolerable for a race horse. Also, the active rubbing together of the rivet shank and rivet head on the pad can cause undesirable wear on the pad and lead to premature separation.
It is an object of this invention to provide a metal horseshoe with a plastic pad adhesively attached to it with an additional retention means to withstand both peeling separation and shear forces, but without requiring a third discontinuous element of dissimilar physical characteristics such as a metal rivet.
An improved horseshoe according to this invention includes a metal shoe having a general U shape including a central bight and an arm extending from each end of the bight. Each arm has a tip. The shoe includes a flat surface and an opposite wear surface with appropriate ground- engaging elements such as grooves or cleats as appropriate. Openings through the metal shoe pass nails which are driven through them into the hoof to hold the shoe in place. A flat organic plastic pad with two oppositely facing flat surfaces is laid upon and cemented to the flat surface of the shoe, intended to bear against the hoof when the animal is shod. The nails are driven through this pad.
According to a preferred feature of this invention, the pad includes a stud of like material integral with the rest of the pad and projecting from one of its flat faces. The flat surface of the metal shoe includes a recess having substantially the same lateral dimensions as the stud, and the pad and the stud are cemented respectively to the flat surface and to the wall of the recess.
According to an optional feature of the invention, the stud, instead of being formed unitary with the pad, is a separated body cemented to the pad, preferably made of like material.
The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which: